Article of footwear with upper and sole structure having substantially equal coefficients of friction

ABSTRACT

An article of footwear comprises an upper and a sole structure secured to the upper. The upper includes a side portion that has a first material composition at an exterior surface of the side portion. The exterior surface has a first coefficient of friction. The sole structure has a second material composition at an exterior surface of the sole structure that underlies the side portion of the upper. The exterior surface of the sole structure has a second coefficient of friction. The first coefficient of friction is substantially equal to the second coefficient of friction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/552,534, filed Aug. 31, 2017, which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present teachings generally include an article of footwear having anupper and a sole structure that have different material compositions butsubstantially equal coefficients of friction.

BACKGROUND

The various components of an article of footwear serve differentfunctions. Accordingly, different footwear components are often made ofdifferent materials best suited for their different functions. Theeffectiveness of footwear used for skateboarding is dependent of thesometimes competing goals of flexibility, energy absorption, fit,durability, and grip. Flexible footwear enhances the wearer's ability toquickly sense and adjust the position of his or her feet as desired onthe skateboard. Energy absorption limits the transfer of high impactloads to the foot. Fit ensures that the footwear doesn't move relativeto the foot during use so that control of the skateboard via movementsof the foot is most accurately conveyed to the skateboard. Durability isimportant due to frequent contact of the footwear with the abrasivesurfaces of the skateboard and with concrete. Grip is desirable toenhance the wearer's ability to control the skateboard with his or herfeet.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only, areschematic in nature, and are intended to be exemplary rather than tolimit the scope of the disclosure.

FIG. 1 is a schematic illustration in medial side view of an article offootwear having an upper and a sole structure.

FIG. 2 is a schematic illustration in lateral side view of the articleof footwear of FIG. 1.

FIG. 3 is a schematic perspective illustration of the article offootwear of FIG. 1 showing a bottom of the sole structure and a medialside of the upper.

FIG. 4 is a schematic illustration in medial side view of the article offootwear of FIG. 1 showing a partial cut-away of an outer unit of theupper.

FIG. 5 is a schematic plan view illustration of the outer unit of theupper of FIG. 1 prior to assembly to the sole structure.

FIG. 6 is a schematic cross-sectional illustration of the outer unit ofthe upper taken at lines 6-6 in FIG. 5.

FIG. 7 is a schematic fragmentary cross-sectional illustration of theouter unit of the upper taken at lines 7-7 in FIG. 5.

FIG. 8 is a schematic illustration in front perspective view of thearticle of footwear of FIG. 1 with a side portion of the upper and asidewall of the sole structure contacting an object shown in phantom.

FIG. 9 is a schematic illustration in front perspective view of thearticle of footwear of FIG. 1 with a bottom of the sole structurecontacting the object shown in phantom.

DESCRIPTION

An article of footwear particularly suited for controlling an object incontact with an exterior surface of the article of footwear has an upperand a sole structure of different material compositions butsubstantially equal coefficients of friction. The article of footwearmay enhance a wearer's ability to control an object in contact with thearticle of footwear as a frictional force exerted by the wearer via thearticle of footwear will be somewhat independent of the location ofcontact of the object (i.e., will be the same if the location is theupper or the sole structure).

An article of footwear comprises an upper and a sole structure securedto the upper. The upper includes a side portion that has a firstmaterial composition at an exterior surface of the side portion. Theexterior surface has a first coefficient of friction. The sole structurehas a second material composition at an exterior surface of the solestructure that underlies the side portion of the upper. The exteriorsurface of the sole structure has a second coefficient of friction. Thefirst coefficient of friction is substantially equal to the secondcoefficient of friction. Accordingly, surface contact with the exteriorportion of the side portion of the upper will provide substantially thesame grip and feel as surface contact with the exterior portion of thesole structure. Motions in which an object is contacted with theexterior surface of the side portion of the upper followed by contactwith the exterior surface of the sole structure, or vice versa, canprovide identical grip on the object in both phases, allowing movementto be made seamlessly between the two surfaces. The object may be anyobject to be controlled by the footwear 10, such as a skateboard or aball. For example, control of the object may be improved due to thenearly identical frictional forces that may result regardless of whetherthe skateboard is in contact with the side surface of the upper or is incontact with the sole structure. Such control may be achieved eventhough the upper and the sole structure have different materialcompositions as may be desirable in order to achieve their respectivefunctions, such as comfort and ventilation of the upper and cushioningand durability of the sole structure. For example, the upper may have atleast one of eyelet openings or ventilation openings. The first materialcomposition may include rubber, such as natural rubber or syntheticrubber, but is not limited to such. The second material composition mayinclude polymeric foam but is not limited to such. Non-limiting examplesof materials from which the first material composition and the secondmaterial composition may be selected include rubber, a polymeric foam,silicone, thermoplastic polyurethane, polypropylene, polyethylene,ethylvinvlyacetate, and styrene ethylbutylene styrene, for example, andcombinations of such, with the first material composition and the secondmaterial composition being different, however.

In one or more embodiments, the sole structure has a side wall, and theexterior surface of the sole structure is at the side wall. In suchembodiments, the sole structure has a bottom with a bottom surface. Thebottom surface may be contiguous with the exterior surface of the sidewall and may also have the second coefficient of friction.

In one or more embodiments, the upper may include an outer layer and aninner layer. The outer layer may include the side portion with theexterior surface. The inner layer may be bonded to an inner surface ofthe outer layer. The inner layer may have a third material compositionthat is softer than the first material composition. For example, theinner layer may be a textile, while the outer layer may be rubber.

In one or more embodiments, the upper includes both an outer unit and aninner unit. The outer unit has a forefoot region, a midfoot region, aheel region, and includes the side portion with the exterior surface.The outer unit is a one-piece, unitary component. In such embodiments,the upper may include an inner unit disposed inward of the outer unitand defining a foot-receiving cavity. The outer unit may be securablearound the foot-receiving cavity separately from the inner unit. Forexample, the inner unit may be a sock configuration that secures aroundthe foot when the foot is inserted therein, while the outer unit mayhave eyelet openings for one or more laces, or may have other fasteningmechanisms to secure the outer unit around the foot.

In one or more embodiments, the article of footwear further comprisestensioning cables secured to the sole structure and disposed between theouter unit and the inner unit. The outer unit has eyelet openings, andthe tensioning cables form loops remote from the sole structure. Theloops are configured to be disposed adjacent to the eyelet openings. Forexample, a lace may be inserted through the eyelet openings while alsopassing through the loops so that tightening the lace willsimultaneously tighten the outer unit around the foot and tighten thetensioning cables around the foot.

In one or more embodiments, the upper has a forefoot region that has atoe box region and a vamp region contiguous with the toe box region. Thetoe box region is adjacent to the sole structure and between the solestructure and the vamp region. The toe box region has a first thickness,and the vamp region has a second thickness less than the firstthickness. Accordingly, the toe box region is sufficiently thick tosupport and protect the front and sides of the toes of a foot insertedin the foot-receiving cavity of the upper, while the vamp region issufficiently thin to encourage flexing, and is well suited forventilation openings.

In one or more embodiments, a boundary between the vamp region and thetoe box region extends around the forefoot region of the upper from amedial side of the upper to a lateral side of the upper. The upper mayflex at a boundary between the vamp region and the toe box region undera force applied to a bottom surface of the sole structure.

In one or more embodiments, the toe box region and the vamp region areboth of the first material composition. The exterior surface of the sideportion in the toe box region having the first coefficient of frictionis contiguous with an exterior surface of the vamp region, and theexterior surface of the vamp region also has the first coefficient offriction.

Within the scope of the present disclosure, an article of footwearcomprises an upper including a one-piece, unitary outer unit that has aforefoot region, a midfoot region, and a heel region. The outer unit iscomprised of rubber and has a side portion with an exterior surface thathas a first coefficient of friction. The article of footwear furthercomprises a sole structure secured to the upper. The sole structure iscomprised of polymeric foam and has an exterior surface that has asecond coefficient of friction and that underlies the exterior surfaceof the side portion of the outer unit. The first coefficient of frictionis substantially equal to the second coefficient of friction. Theforefoot region of the outer unit has a toe box region and a vampregion. The toe box region is adjacent to the sole structure and betweenthe sole structure and the vamp region. The toe box region has a firstthickness, and the vamp region has a second thickness less than thefirst thickness.

In one or more embodiments, the outer unit has at least one of eyeletopenings or ventilation openings.

In one or more embodiments, a boundary between the vamp region and thetoe box region extends around the forefoot region of the outer unit froma medial side of the outer unit to a lateral side of the outer unit. Theupper flexes at the boundary under a force applied to a bottom surfaceof the sole structure due to the reduction of thickness at the boundary.

In one or more embodiments, the outer unit includes an outer layer andan inner layer. The inner layer is bonded to an inner surface of theouter layer. The outer layer includes the side portion and the exteriorsurface. The inner layer comprises a textile.

In one or more embodiments, the article of footwear further comprises abootie disposed inward of the outer unit. The bootie defines afoot-receiving cavity. The outer unit is securable around thefoot-receiving cavity separately from the bootie.

In one or more embodiments, the article of footwear further comprisestensioning cables secured to the sole structure and disposed between theouter unit and the bootie. The outer unit has eyelet openings. Thetensioning cables form loops remote from the sole structure. The loopsare configured to be disposed adjacent to the eyelet openings.

The above features and advantages and other features and advantages ofthe present teachings are readily apparent from the following detaileddescription of the modes for carrying out the present teachings whentaken in connection with the accompanying drawings.

Referring to the drawings, wherein like reference numbers refer to likecomponents throughout the views, FIG. 1 shows a medial side view of anarticle of footwear 10. The article of footwear 10 includes an upper 14and a sole structure 18 secured to the upper 14. The upper 14 and thesole structure 18 together define a foot-receiving cavity 16. The solestructure underlies the upper 14 and a foot 19 disposed in afoot-receiving cavity 16 (foot 19 shown in phantom in FIGS. 8 and 9). Asfurther described herein, the upper 14 and sole structure 18 haveexterior surfaces of different material compositions that neverthelessprovide coefficients of friction that are substantially equal so thatsurface contact with the exterior portion of the side portion of theupper 14 will provide the same grip and feel as surface contact with theexterior portion of the sole structure 18.

Referring to FIG. 1, the article of footwear 10 includes a solestructure 18 that underlies the upper 14. The sole structure 18 is shownas a single, one-piece, unitary midsole and outsole, but the solestructure 18 of the article of footwear 10 may have any configurationwithin the scope of the present teachings. For example, the solestructure 18 may include one or more sole components that may beseparate sole layers, such as an outsole and one or more midsole layers.In further configurations, the sole structure 18 may incorporatefluid-filled chambers, plates, moderators, or other elements thatfurther attenuate forces, enhance stability, or influence the motions ofthe foot. In one non-limiting example, the sole structure 18 as shown asa unitary midsole and outsole and may be formed from a compressiblepolymeric foam (e.g., a polyurethane or ethylvinylacetate foam) thatattenuates reaction forces (i.e., provides cushioning) when compressedbetween the foot and an object such as a skateboard or the ground duringwalking, running, or other ambulatory activities.

The upper 14 is secured to the sole structure 18. For example, a lowerextremity of the upper 14 may be bonded or otherwise secured to the solestructure 18. A strobel (not shown) may be secured to the lowerextremity of the upper 14 and to the sole structure 18. An insole (notshown) may overlie the sole structure 18 within the foot-receivingcavity 16. As further described herein, the upper 14 has an outer unit21 and an inner unit 23. The outer unit 21 is a one-piece, unitarycomponent. The inner unit 23 is interior to the outer unit 21 and has asock configuration, and is also referred to herein as a bootie. A foot19 is inserted into the inner unit 23 at an ankle opening 25, and theinner unit 23 stretches to accommodate and conform to the foot 19. Theouter unit 21 is then separately securable to the foot 19 via a lacingsystem 27 that includes tensioning cables 29 and a lace 31.

The upper 14 is configured to receive and retain the foot 19 in thefoot-receiving cavity 16 so that the foot 19 is supported on the solestructure 18 with the sole structure 18 positioned below the foot 19,and between the foot 19 and an object such as skateboard S in FIGS. 8and 9 and the ground.

The article of footwear 10 has a forefoot portion 20, a midfoot portion22 and a heel portion 24, indicated in FIG. 2. Both the upper 14 and thesole structure 18 extend in and partially define the forefoot portion20, the midfoot portion 22 and the heel portion 24. The article offootwear 10 has a medial side 30 (FIG. 1) and a lateral side 32 (FIG. 2)opposite from the medial side 30. The medial side 30 and the lateralside 32 extend through each of forefoot region 20, the midfoot region22, and the heel region 24 and correspond with opposite sides of thearticle of footwear 10. The forefoot region 20, the midfoot region 22,the heel region 24, the medial side 30 and the lateral side 32 are notintended to demarcate precise areas of footwear 10, but are insteadintended to represent general areas of the article footwear 10 to aid inthe discussion. The article of footwear 10 shown in configured for aright foot. An article of footwear for a left foot has a mirror image ofthat shown, and is within the scope of the present teachings.

The upper 14 includes a side portion 34 that has a first materialcomposition at an exterior surface 35 of the side portion 34. Theexterior surface 35 has a first coefficient of friction μ₁. The exteriorsurface 35 that has the first coefficient of friction μ₁ may be theentire side portion 34, or only selected areas of the side portion 34may have the exterior surface 35 with the first coefficient of frictionμ₁. In the embodiment shown, the entire side portion 34 is of the firstmaterial composition and has the exterior surface 35 with the firstcoefficient of friction μ₁. The side portion 37 at the lateral side 32also has an exterior surface 47 that has the first coefficient offriction μ₁. It should be appreciated that the exterior surface 47 maybe textured, with the texture contributing to the coefficient offriction.

The first material composition may comprise a natural or syntheticrubber, for example. The first material composition is selected toprovide the first coefficient of friction μ₁ which is that of a rubberthat is sufficiently soft to provide good grip. It should be appreciatedthat the exterior surface 35 with the first material composition may betextured, with the texture contributing to the first coefficient offriction μ₁.

The upper 14 includes eyelet openings 50 and ventilation openings 52that extend entirely through the outer unit 21. For example, as shown inFIG. 5, eyelet openings 50 extend on either side of the tongue 39.Ventilation openings 52 are shown in a vamp region 38, but may insteador in addition be in a toe box region 36, or further rearward in themidfoot region 22 or heel region 24. Accordingly, the first materialcomposition at the exterior surface 35 meets frictional and durabilityrequirements while providing comfort and ventilation of the upper 14.The first composition is not limited to a material that includes rubber,and the upper 14 may be a variety of materials, such as leather,textiles, polymers, cotton, foam, composites, etc., as long as theexterior surface of the sole structure 18 underlying the exteriorsurface 35 is of a different second material composition.

With reference to FIGS. 1 and 5, the outer unit 21 of the upper 14 has atoe box region 36 and a vamp region 38 contiguous with the toe boxregion 36. The toe box region 36 is in the forefoot region 20. The vampregion 38 extends in both the forefoot region 20 and the midfoot region22. With reference to FIG. 1, the toe box region 36 is adjacent to thesole structure 18 and between the sole structure 18 and the vamp region38. The toe box region 36 is configured to extend over the toes of awearer and around the front of the toes, as well as on the medial side30 of the big toe and on the lateral side 32 of the little toe. The toebox region 36 may also be referred to as the toe region.

The vamp region 38 is configured to extend over the instep of the foot19, and is bounded by the toe box region 36 forward of the vamp region38, and below the vamp region 38 at the medial side 30 and at thelateral side 32. The vamp region 38 extends rearward from the forefootregion 20 into the midfoot region 22, and includes a tongue 39. Aboundary 40 between the vamp region 38 and the toe box region 36 extendsaround the forefoot region 20 of the upper 14 from the medial side 30 tothe lateral side 32. With reference to FIG. 5, the toe box region 36 isbounded by an outer perimeter P of the upper 14, the boundary 40, and aboundary 41 that is generally configured to fall along themetatarsophalangeal joints of the foot 19. The toe box region 36 isentirely in the forefoot region 20.

In the embodiment shown, the toe box region 36 and the vamp region 38are both of the first material composition. The exterior surface 35 ofthe side portion 34 is in the toe box region 36. The exterior surface 35of the side portion 34 is contiguous with an exterior surface 42 of thevamp region 38. The exterior surface 42 of the vamp region 38 also hasthe first coefficient of friction μ₁.

The sole structure 18 is configured to work in conjunction with theupper 14 to provide a seamless grip at both the exterior surface 35 ofthe side portion 34 of the upper 14 and the sole structure 18. In one ormore embodiments, the sole structure 18 has a side wall 54 as well as abottom 60. The side wall 54 has an exterior surface 58 that directlyunderlies the exterior surface 35 of the side portion 34 of the upper14. The sole structure has a second material composition at the exteriorsurface 58. The second material composition is different from the firstmaterial composition of the upper 14. For example, in the embodimentshown, the second material composition is polymeric foam. Non-limitingexamples of materials from which the first material composition and thesecond material composition may be selected include rubber, a polymericfoam, silicone, thermoplastic polyurethane, polypropylene, polyethylene,ethylvinvlyacetate, and styrene ethylbutylene styrene, for example, andcombinations of such, with the first material composition and the secondmaterial composition being different, however.

The exterior surface 58 of the sole structure 18 has a secondcoefficient of friction μ₂. As used herein, the first coefficient offriction μ₁ and the second coefficient of friction μ₂ are dimensionless,and may both be coefficients of static friction, or may both becoefficients of kinetic friction. The first coefficient of friction μ₁and the second coefficient of friction μ₂ are determined according tothe same test, using the same reference object, such as according to anystandard ASTM test. Ideally, the first coefficient of friction μ₁ andthe second coefficient of friction μ₂ are equal. However, a range ofvariance is possible due to manufacturing tolerances or otherwise. Inall cases, the first coefficient of friction μ₁ is equal or“substantially equal” to the second coefficient of friction μ₂. As usedherein, the first coefficient of friction μ₁ is “substantially equal” tothe second coefficient of friction μ₂ when the difference between thefirst coefficient of friction μ₁ and the second coefficient of frictionμ₂ is not more than 20 percent of the first coefficient of friction μ₁.Stated differently, the second coefficient of friction μ₁ is within therange from 20 percent less than to 20 percent greater than the firstcoefficient of friction μ₁. In some embodiments, the difference betweenthe first coefficient of friction μ₁ and the second coefficient offriction μ₂ is not more than 15 percent of the first coefficient offriction μ₁. In some embodiments, the difference between the firstcoefficient of friction μ₁ and the second coefficient of friction μ₂ isnot more than 10 percent of the first coefficient of friction μ₁. Insome embodiments, the difference between the first coefficient offriction μ₁ and the second coefficient of friction μ₂ is not more than 5percent of the first coefficient of friction μ₁. In some embodiments,the difference between the first coefficient of friction μ₁ and thesecond coefficient of friction μ₂ is not more than 2 percent of thefirst coefficient of friction μ₁. In some embodiments, the differencebetween the first coefficient of friction μ₁ and the second coefficientof friction μ₂ is not more than 1 percent of the first coefficient offriction μ₁. Accordingly, the difference between the first coefficientof friction μ₁ and the second coefficient of friction μ₂ can be any oneof, but is not limited to, 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%,11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, inclusive ofvalues therebetween.

In the embodiment shown, the entire exterior surface of the side wall54, including the exterior surface in the forefoot region 20, theexterior surface in the midfoot region 22, and the exterior surface inthe heel region 24 and of both the medial side 30 and the lateral side32 is of the second material composition that has the second coefficientof friction μ₂. Configuring the sole structure 18 so that the side wall54 has the second coefficient of friction μ₂ enables the entire exposedmedial side 30 and the entire exposed lateral side 32 of the article offootwear 10 to present substantially the same coefficient of friction toan object such as a skateboard. Control of a skateboard is illustratedin FIGS. 8 and 9, but it should be appreciated that control of anyobject may be improved in the same manner as discussed with respect tothe skateboard. Although described as an article of footwear 10 forskateboarding, the upper 14 and sole structure 18 are not solely limitedto footwear designed for skateboarding, however, and may be incorporatedinto a wide range of athletic footwear styles, including shoes that aresuitable for baseball, basketball, cross-training, football, rugby,soccer, tennis, volleyball, and walking, for example. In addition, thefootwear 10 with upper 14 and sole structure 18 as described may befootwear that is generally considered to be non-athletic footwear,including a variety of dress shoes, casual shoes, sandals, and boots.

Surface contact with the exterior surface 35 of the upper 14 willprovide the same grip and feel as surface contact with the exteriorsurface 58 of the side wall 54 of the sole structure 18. Motions inwhich an object is contacted with the exterior surface 35 of the upper14 followed by contact with the exterior surface 58 of the side wall 54,or vice versa, can provide identical grip on the object in both phases,allowing movement to be made seamlessly between the two surfaces. Forexample, control of a skateboard S may be improved due to the nearlyidentical frictional forces F1, F2 that may result on the exteriorsurface 35 of the upper 14 and on the exterior surface 58 of the solestructure 18 regardless of whether the skateboard S is in contact withthe exterior surface 35 of the upper 14 or is in contact with theexterior surface 58 of the side wall 54. In FIG. 8, the skateboard S isshown simultaneously in contact with both the exterior surface 35 of theupper 14 and the exterior surface 58 of the sole structure 18.Accordingly, control of the skateboard S remains consistent whether theskateboard S is in contact with the upper 14, with the sole structure18, or with both. During movements in which contact transitions from theupper 14 to the sole structure 18 or vice versa, the force that thewearer must apply to the skateboard to result in a given grip (i.e., agiven friction force F1 or F2) remains consistent. For example, theskateboard S may slide across the footwear 10 from the upper 14 to thesole structure 18 or vice versa without any variance in applied force bythe wearer required to result in the same frictional force on theskateboard S. In another example, if the skateboard S moves out ofcontact with the upper 14 and then back into contact with the solestructure 18, or vice versa, the same applied force by the wearer isrequired to result in the same frictional force on the skateboard S.

The sole structure 18 also has a bottom 60 with a bottom surface 62 bestshown in FIGS. 3 and 8. In the article of footwear shown, the side wall54 and the bottom 60 form a right angle with one another or an anglewithin 5 degrees of a right angle. More particularly, the edge of theintersection of the side wall 54 and the bottom 60 may be rounded, but aplane generally coincident with the exterior surface 58 of the side wall54 and a plane generally coincident with the bottom surface 62 form aright angle or are substantially a right angle, such as within 5 degreesof a right angle. The bottom surface 62 is contiguous with the exteriorsurface 58 of the side wall 54. As shown in FIG. 3, the bottom surface62 may include some grooves 64 or siping for increased traction. Thebottom 60 is of the same second material composition as the side wall 54in the embodiment shown, or may be of a different material composition.In either case, the bottom surface 62 may be configured to have thesecond coefficient of friction, at least in areas between the sipes 64,areas without siping, or in areas where the sipes 64 do not affect thecoefficient of friction.

The substantially identical coefficients of friction and the resultingsubstantially identical frictional forces that may be applied to controlthe skateboard S are possible even though the upper 14 and the solestructure 18 have different material compositions as may be desirable inorder to achieve their respective functions. For example, a polymericfoam of the sole structure 18 provides desired cushioning anddurability, while a rubber of the upper 14 is relatively comfortable andflexible. Additionally, the rubber of the upper 14 is sufficientlystrong to withstand forces that may be applied by the lace 31 at thelace openings 50, and is easily provided with ventilation openings 52 bymolding, piercing, punching, or otherwise.

As a rubber outer unit 21 is less able to automatically conform to thefoot 19 than the inner unit 23, tensioning cables 29 are used to helpprovide medial and lateral support. The tensioning cables 29 form loops66 remote from the sole structure 18 as shown in FIG. 4. The tensioningcables 29 are configured with a length such that the loops 66 aredisposed adjacent to the eyelet openings 50. The lace 31 may be insertedthrough the eyelet openings 50 while also passing through the loops 66so that tightening the lace 31 will simultaneously tighten the outerunit 21 around the foot while tightening the tensioning cables 29 aroundthe foot 19. The separate inner unit 23 is not secured to the innersurface of the outer unit 21, and so can be configured to snugly receivethe foot 19. The inner unit 23 in combination with the cables 29 helpsto prevent unwanted movement of the foot 19 relative to the solestructure 18 within the foot-receiving cavity 16.

As best shown in FIGS. 6 and 7, the outer unit 21 of the upper 14 mayinclude an outer layer 70 and an inner layer 72. The outer layer 70includes the side portion 34 with the exterior surface 35. The innerlayer 72 may be secured to an inner surface 74 of the outer layer 70such as by adhesive or by thermal bonding with or without adhesive. Theinner layer 72 may have a third material composition that is softer thanthe first material composition. For example, the inner layer 72 may be atextile. The inner layer 72 lines the inner surface of the outer layer70 and presents softer material to be exposed to the inner unit 23adjacent to the foot 19. Softness may be measured on a hardness scale.For example, softness may be measured according to an ASTM test forShore A hardness. Generally, softer materials tend to provide a highercoefficient of friction and a corresponding better grip. Materials witha higher surface texture may also provide a higher coefficient offriction.

With reference to FIG. 7, the toe box region 36 has a first thicknessT1, and the vamp region 38 has a second thickness T2 less than the firstthickness T1. To achieve the different thicknesses, the outer layer 70may be molded, for example. Accordingly, the thickness T1 of the toe boxregion 36 is configured to be sufficiently thick so that the toe boxregion 36 supports and protect the front and sides of the toes of a foot19 inserted in the foot-receiving cavity 16 of the upper 14. Thethickness T2 of the vamp region 38 is configured to be sufficiently thinto encourage flexing and to be well suited for ventilation openings.More specifically, because a thicker component is more difficult to bendthan a thinner component of the same material, due to the thicknessdifferential between the toe region 36 and the vamp region 38, the upper14 may flex at the boundary 40 between the vamp region 38 and the toebox region 36, such as under a force F3 applied to the bottom surface 62of the sole structure 18 as shown in FIG. 9. FIG. 9 illustrates a bend Bof the outer unit 21 at the boundary 40 that occurs under loading by theforce F3 and by a force F4 on the outer unit by the foot 19 as thewearer bends at the ankle during a control maneuver. At the bend B, theouter unit 21 buckles or folds slightly over on itself, with a bendangle A having a vertex V at the boundary 40.

Thus, the substantially equal first and second coefficients of frictionwill provide a skateboarder with improved feel when manipulating askateboard.

The following Clauses provide example configurations of an article offootwear disclosed herein.

Clause 1: An article of footwear comprising: an upper including a sideportion that has a first material composition at an exterior surface ofthe side portion, the exterior surface having a first coefficient offriction; and a sole structure secured to the upper and having a secondmaterial composition at an exterior surface of the sole structureunderlying the side portion of the upper, the exterior surface of thesole structure having a second coefficient of friction; wherein thefirst coefficient of friction is substantially equal to the secondcoefficient of friction.

Clause 2: The article of footwear of Clause 1, wherein: the solestructure has a side wall; and the exterior surface of the solestructure is at the side wall.

Clause 3: The article of footwear of Clause 2, wherein: the solestructure has a bottom with a bottom surface; the bottom surface iscontiguous with the exterior surface of the side wall; and the bottomsurface has the second coefficient of friction.

Clause 4: The article of footwear of any of Clauses 1-3, wherein theupper has at least one of eyelet openings or ventilation openings.

Clause 5: The article of footwear of any of Clauses 1-4, wherein thefirst material composition includes rubber.

Clause 6: The article of footwear of Clause 5, wherein the secondmaterial composition includes polymeric foam.

Clause 7: The article of footwear of any of Clauses 1-6, wherein: theupper includes an outer layer and an inner layer; the outer layerincludes the side portion with the exterior surface; the inner layer isbonded to an inner surface of the outer layer; and the inner layer has athird material composition that is softer than the first materialcomposition.

Clause 8: The article of footwear of any of Clauses 1-7, wherein: theupper includes an outer unit that has a forefoot region, a midfootregion, a heel region, and the side portion with the exterior surface;and the outer unit is a one-piece, unitary component.

Clause 9: The article of footwear of Clause 8, wherein the upperincludes an inner unit disposed inward of the outer unit and defining afoot-receiving cavity; and wherein the outer unit is securable aroundthe foot-receiving cavity separately from the inner unit.

Clause 10: The article of footwear of Clause 9, further comprising:tensioning cables secured to the sole structure and disposed between theouter unit and the inner unit; wherein the outer unit has eyeletopenings; and wherein the tensioning cables form loops remote from thesole structure and configured to be disposed adjacent to the eyeletopenings.

Clause 11: The article of footwear of any of Clauses 1-10, wherein: theupper has a forefoot region that includes a toe box region and a vampregion contiguous with the toe box region; the toe box region isadjacent to the sole structure and between the sole structure and thevamp region; the toe box region has a first thickness; and the vampregion has a second thickness less than the first thickness.

Clause 12: The article of footwear of Clause 11, wherein a boundarybetween the vamp region and the toe box region extends around theforefoot region of the upper from a medial side of the upper to alateral side of the upper.

Clause 13: The article of footwear of Clause 11, wherein: the upperflexes at a boundary between the vamp region and the toe box regionunder a force applied to a bottom surface of the sole structure.

Clause 14: The article of footwear of Clause 11, wherein the toe boxregion and the vamp region are both of the first material composition;the exterior surface of the side portion is in the toe box region; theexterior surface of the side portion is contiguous with an exteriorsurface of the vamp region; and the exterior surface of the vamp regionhas the first coefficient of friction.

Clause 15: An article of footwear comprising: an upper including aone-piece, unitary outer unit that has a forefoot region, a midfootregion, and a heel region; wherein the outer unit is comprised of rubberand has a side portion with an exterior surface that has a firstcoefficient of friction; a sole structure secured to the upper; whereinthe sole structure is comprised of polymeric foam and has an exteriorsurface that has a second coefficient of friction and that underlies theexterior surface of the side portion of the outer unit; wherein thefirst coefficient of friction is substantially equal to the secondcoefficient of friction; and wherein the forefoot region of the outerunit has a toe box region and a vamp region, the toe box region isadjacent to the sole structure and between the sole structure and thevamp region, the toe box region has a first thickness, and the vampregion has a second thickness less than the first thickness.

Clause 16: The article of footwear of Clause 15, wherein the outer unithas at least one of eyelet openings or ventilation openings.

Clause 17: The article of footwear of any of Clauses 15-16, wherein: aboundary between the vamp region and the toe box region extends aroundthe forefoot region of the outer unit from a medial side of the outerunit to a lateral side of the outer unit; and the upper flexes at theboundary under a force applied to a bottom surface of the solestructure.

Clause 18: The article of footwear of any of Clauses 15-17, wherein: theouter unit includes an outer layer and an inner layer; the inner layeris bonded to an inner surface of the outer layer; the outer layerincludes the side portion and the exterior surface; and the inner layercomprises a textile.

Clause 19: The article of footwear of any of Clauses 15-18, furthercomprising: a bootie disposed inward of the outer unit and defining afoot-receiving cavity; and wherein the outer unit is securable aroundthe foot-receiving cavity separately from the bootie.

Clause 20: The article of footwear of Clause 19, further comprising:tensioning cables secured to the sole structure and disposed between theouter unit and the bootie; wherein the outer unit has eyelet openings;and wherein the tensioning cables form loops remote from the solestructure and configured to be disposed adjacent to the eyelet openings.

To assist and clarify the subsequent description of various embodiments,various terms are defined herein. Unless otherwise indicated, thefollowing definitions apply throughout this specification (including theclaims).

An “article of footwear”, a “footwear article of manufacture”, and“footwear” may be considered to be both a machine and a manufacture.Assembled, ready to wear footwear articles (e.g., shoes, sandals, boots,etc.), as well as discrete components of footwear articles (such as amidsole, an outsole, an upper component, etc.) prior to final assemblyinto ready to wear footwear articles, are considered and alternativelyreferred to herein in either the singular or plural as “article(s) offootwear”.

“A”, “an”, “the”, “at least one”, and “one or more” are usedinterchangeably to indicate that at least one of the items is present. Aplurality of such items may be present unless the context clearlyindicates otherwise. All numerical values of parameters (e.g., ofquantities or conditions) in this specification, unless otherwiseindicated expressly or clearly in view of the context, including theappended claims, are to be understood as being modified in all instancesby the term “about” whether or not “about” actually appears before thenumerical value. “About” indicates that the stated numerical valueallows some slight imprecision (with some approach to exactness in thevalue; approximately or reasonably close to the value; nearly). If theimprecision provided by “about” is not otherwise understood in the artwith this ordinary meaning, then “about” as used herein indicates atleast variations that may arise from ordinary methods of measuring andusing such parameters. In addition, a disclosure of a range is to beunderstood as specifically disclosing all values and further dividedranges within the range. All references referred to are incorporatedherein in their entirety.

The terms “comprising”, “including”, and “having” are inclusive andtherefore specify the presence of stated features, steps, operations,elements, or components, but do not preclude the presence or addition ofone or more other features, steps, operations, elements, or components.Orders of steps, processes, and operations may be altered when possible,and additional or alternative steps may be employed. As used in thisspecification, the term “or” includes any one and all combinations ofthe associated listed items. The term “any of” is understood to includeany possible combination of referenced items, including “any one of” thereferenced items. The term “any of” is understood to include anypossible combination of referenced claims of the appended claims,including “any one of” the referenced claims.

For consistency and convenience, directional adjectives are employedthroughout this detailed description corresponding to the illustratedembodiments. Those having ordinary skill in the art will recognize thatterms such as “above”, “below”, “upward”, “downward”, “top”, “bottom”,etc., may be used descriptively relative to the figures, withoutrepresenting limitations on the scope of the invention, as defined bythe claims.

The term “longitudinal”, as used throughout this detailed descriptionand in the claims, refers to a direction extending a length of acomponent. For example, a longitudinal direction of a shoe extendsbetween a forefoot region and a heel region of the shoe. The term“forward” is used to refer to the general direction from a heel regiontoward a forefoot region, and the term “rearward” is used to refer tothe opposite direction, i.e., the direction from the forefoot regiontoward the heel region. In some cases, a component may be identifiedwith a longitudinal axis as well as a forward and rearward longitudinaldirection along that axis.

The term “vertical”, as used throughout this detailed description and inthe claims, refers to a direction generally perpendicular to both thelateral and longitudinal directions. For example, in cases where a soleis planted flat on a ground surface, the vertical direction may extendfrom the ground surface upward. It will be understood that each of thesedirectional adjectives may be applied to individual components of asole. The term “upward” or “upwards” refers to the vertical directionpointing towards a top of the component, which may include an instep, afastening region and/or a throat of an upper. The term “downward” or“downwards” refers to the vertical direction pointing opposite theupwards direction, and may generally point towards the sole, or towardsthe outermost components of the sole.

The “interior” of an article of footwear, such as a shoe, refers toportions at the space that is occupied by a wearer's foot when the shoeis worn. The “inner side” of a component refers to the side or surfaceof the component that is (or will be) oriented toward the interior ofthe shoe in an assembled shoe. The “outer side” or “exterior” of acomponent refers to the side or surface of the component that is (orwill be) oriented away from the interior of the shoe in an assembledshoe. In some cases, the inner side of a component may have othercomponents between that inner side and the interior in the assembledshoe. Similarly, an outer side of a component may have other componentsbetween that outer side and the space external to the assembled shoe.Further, the terms “inward” and “inwardly” shall refer to the directiontoward the interior of the component or article of footwear, such as ashoe, and the terms “outward” and “outwardly” shall refer to thedirection toward the exterior of the component or article of footwear,such as the shoe. In addition, the term “proximal” refers to a directionthat is nearer a center of a footwear component, or is closer toward afoot when the foot is inserted in the article as it is worn by a user.Likewise, the term “distal” refers to a relative position that isfurther away from a center of the footwear component or is further froma foot when the foot is inserted in the article as it is worn by a user.Thus, the terms proximal and distal may be understood to providegenerally opposing terms to describe the relative spatial position of afootwear layer.

While various embodiments have been described, the description isintended to be exemplary, rather than limiting and it will be apparentto those of ordinary skill in the art that many more embodiments andimplementations are possible that are within the scope of theembodiments. Any feature of any embodiment may be used in combinationwith or substituted for any other feature or element in any otherembodiment unless specifically restricted. Accordingly, the embodimentsare not to be restricted except in light of the attached claims andtheir equivalents. Also, various modifications and changes may be madewithin the scope of the attached claims.

While several modes for carrying out the many aspects of the presentteachings have been described in detail, those familiar with the art towhich these teachings relate will recognize various alternative aspectsfor practicing the present teachings that are within the scope of theappended claims. It is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and exemplary of the entire range of alternativeembodiments that an ordinarily skilled artisan would recognize asimplied by, structurally and/or functionally equivalent to, or otherwiserendered obvious based upon the included content, and not as limitedsolely to those explicitly depicted and/or described embodiments.

What is claimed is:
 1. An article of footwear comprising: an upperincluding a side portion that has a first material composition at anexterior surface of the side portion, the exterior surface having afirst coefficient of friction; and a sole structure secured to the upperand having a side wall underlying the side portion of the upper, anexterior surface of the side wall having a second material compositiondifferent than the first material composition; the exterior surface ofthe side wall having a second coefficient of friction; wherein the firstcoefficient of friction is substantially equal to the second coefficientof friction.
 2. The article of footwear of claim 1, wherein: the solestructure has a bottom with a bottom surface; the bottom surface iscontiguous with the exterior surface of the side wall; and the bottomsurface has the second coefficient of friction.
 3. The article offootwear of claim 1, wherein the upper has at least one of eyeletopenings or ventilation openings.
 4. The article of footwear of claim 1,wherein the first material composition includes rubber.
 5. The articleof footwear of claim 4, wherein the second material composition includespolymeric foam.
 6. The article of footwear of claim 1, wherein: theupper includes an outer layer and an inner layer; the outer layerincludes the side portion with the exterior surface; the inner layer isbonded to an inner surface of the outer layer; and the inner layer has athird material composition that is softer than the first materialcomposition.
 7. The article of footwear of claim 1, wherein: the upperincludes an outer unit that has a forefoot region, a midfoot region, aheel region, and the side portion with the exterior surface; and theouter unit is a one-piece, unitary component.
 8. The article of footwearof claim 7, wherein the upper includes an inner unit disposed inward ofthe outer unit and defining a foot-receiving cavity; the article offootwear further comprising a lacing system configured to tighten theouter unit around the inner unit.
 9. The article of footwear of claim 8,further comprising: tensioning cables secured to the sole structure anddisposed between the outer unit and the inner unit; wherein the outerunit has eyelet openings; and wherein the tensioning cables form loopsremote from the sole structure and configured to be disposed adjacent tothe eyelet openings.
 10. The article of footwear of claim 1, wherein:the upper has a forefoot region that includes a toe box region and avamp region contiguous with the toe box region; the toe box region isadjacent to the sole structure and between the sole structure and thevamp region; the toe box region has a first thickness; and the vampregion has a second thickness less than the first thickness.
 11. Thearticle of footwear of claim 10, wherein a boundary between the vampregion and the toe box region extends around the forefoot region of theupper from a medial side of the upper to a lateral side of the upper.12. The article of footwear of claim 10, wherein the toe box region andthe vamp region are both of the first material composition; the exteriorsurface of the side portion is in the toe box region; the exteriorsurface of the side portion is contiguous with an exterior surface ofthe vamp region; and the exterior surface of the vamp region has thefirst coefficient of friction.
 13. An article of footwear comprising: anupper including a one-piece, unitary outer unit that has a forefootregion, a midfoot region, and a heel region; wherein the outer unit iscomprised of rubber and has a side portion with an exterior surface thathas a first coefficient of friction; a sole structure secured to theupper; wherein the sole structure is comprised of polymeric foam and hasan exterior surface that has a second coefficient of friction and thatunderlies the exterior surface of the side portion of the outer unit;wherein the first coefficient of friction is substantially equal to thesecond coefficient of friction; wherein the forefoot region of the outerunit has a toe box region and a vamp region, the toe box region isadjacent to the sole structure and between the sole structure and thevamp region, the toe box region has a first thickness, and the vampregion has a second thickness less than the first thickness; and whereina boundary between the vamp region and the toe box region extends aroundthe forefoot region of the outer unit from a medial side of the outerunit to a lateral side of the outer unit and extends rearward to anankle opening defined by the upper.
 14. The article of footwear of claim13, wherein the outer unit has at least one of eyelet openings orventilation openings.
 15. The article of footwear of claim 13, wherein:the outer unit includes an outer layer and an inner layer; the innerlayer is bonded to an inner surface of the outer layer; the outer layerincludes the side portion and the exterior surface; and the inner layercomprises a textile.
 16. The article of footwear of claim 13, furthercomprising: a bootie disposed inward of the outer unit and defining afoot-receiving cavity; and wherein the outer unit is securable aroundthe foot-receiving cavity separately from the bootie.
 17. The article offootwear of claim 16, further comprising: tensioning cables secured tothe sole structure and disposed between the outer unit and the bootie;wherein the outer unit has eyelet openings; and wherein the tensioningcables form loops remote from the sole structure and configured to bedisposed adjacent to the eyelet openings.
 18. An article of footwearcomprising: an upper; a sole structure secured to and underlying theupper; wherein the upper includes a vamp region having a boundaryextending around a forefoot region of the upper and extending rearwardto an ankle opening in the upper; wherein a thickness of the upperchanges from a first thickness to a second thickness of the vamp regionat the boundary, the second thickness less than the first thickness;wherein the upper has a first material composition at an exteriorsurface of the upper, and the exterior surface of the upper with thefirst material composition has a first coefficient of friction; andwherein the sole structure has a second material composition differentthan the first material composition at an exterior surface of the solestructure directly underlying the exterior surface of the upper that hasthe first coefficient of friction, the exterior surface of the solestructure having a second coefficient of friction, and the firstcoefficient of friction is substantially equal to the second coefficientof friction.
 19. The article of footwear of claim 18, wherein: the solestructure has a side wall; the exterior surface of the sole structurehaving the second material composition and the second coefficient offriction is at the side wall; the sole structure has a bottom with abottom surface; the bottom surface is contiguous with the exteriorsurface of the side wall; and the bottom surface has the secondcoefficient of friction.